Folding knife



FIG. 1 is a front view in elevation of the ornamental design of a folding knife;

FIG. 2 is a view in elevation of the right side of the folding knife shown in FIG. 1;

FIG. 3 is a rear view in elevation of the folding knife shown in FIG. 1;

FIG. 4 is a view in elevation of the left side of the folding knife shown in FIG. 1;

FIG. 5 is a top plan view of the folding knife shown in FIG. 1;

FIG. 6 is a bottom plan view of the folding knife shown in FIG. 1;

FIG. 7 is an isometric view of the folding knife shown in FIG. 1; and,

FIG. 8 is an isometric view of an alternate embodimnent similar to the folding knife shown in FIG. 7. 

The ornamental design for a folding knife, as shown and described. 